Variable geometry helicopter engine inlet

ABSTRACT

A variable area engine inlet of a helicopter is provided and includes first inlet portions disposed to face one another in opposite directions and at a distance from one another and second inlet portions extending between the first inlet portions and being disposed to face one another in opposite directions and at a distance from one another. The first and second inlet portions define a capture area and at least one or both of the first and second inlet portions include a movable portion disposed to occupy and move between first and second positions. The first position is associated with a non-constricted condition of the capture area and the second position is associated with a constricted condition of the capture area.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to a helicopter engine inletand, more particularly, to a helicopter engine inlet with variablegeometry.

A problem with high speed rotorcraft is the need to balance externalaerodynamic performance with engine inlet performance. Larger inletcapture areas are required for higher engine performance at lower speedsand especially hover conditions to permit a greater amount of air toflow into the engine than would be possible at low speeds or hoverconditions with relatively small inlets. These larger inlet captureareas, however, do not provide appreciable engine performance benefit athigher speeds and in many cases act to the detriment of the overallaerodynamic performance of the aircraft. Moreover, the larger inletcapture areas tend to be oversized in the presence of ramming air athigh speeds and thus may result in inlet spillage. Such spillage, whencoupled with the larger exposed surface facing into the freestream flow,may result in higher drag.

Prior solutions for sizing rotorcraft inlets have required that a fixedinlet size be chosen. The fixed inlet size necessitates a performancecompromise in either engine performance at lower speeds and hover,greater aircraft drag at higher speeds or a combination of the two if adesign is chosen in the middle range of inlet sizes.

Other prior solutions have given rise to variable geometry inlets butthese have generally been used only for supersonic fixed wing aircraftand, most often to mitigate supersonic shock.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a variable area engine inletof a helicopter is provided and includes first inlet portions disposedto face one another in opposite directions and at a distance from oneanother and second inlet portions extending between the first inletportions and being disposed to face one another in opposite directionsand at a distance from one another. The first and second inlet portionsdefine a capture area and at least one or both of the first and secondinlet portions include a movable portion disposed to occupy and movebetween first and second positions. The first position is associatedwith a non-constricted condition of the capture area and the secondposition is associated with a constricted condition of the capture area.

According to another aspect of the invention, a helicopter is providedand includes an airframe including a variable area engine inlet, atleast one rotor, which is rotatable relative to the airframe to generatelift and/or thrust and an engine disposed within an interior of theairframe to be receptive of air drawn into the interior through thevariable area engine inlet. The engine is coupled to the at least onerotor to drive rotation of the rotor in accordance with a combustion ofa mixture of fuel and the air. A capture area of the variable areaengine inlet is variable in accordance with current conditions.

According to yet another aspect of the invention, a method ofcontrolling a variable area engine inlet of a helicopter is provided andincludes determining whether a current flight condition is a hover orlow-speed flight condition or a high-speed flight condition,constricting a capture area of the variable area engine inlet in anevent a result of the determining indicates that the current flightcondition is the high-speed flight condition and dilating the capturearea in an event the result of the determining indicates that thecurrent flight condition is the hover or low-speed flight condition.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is a schematic illustration of a helicopter in accordance withembodiments;

FIG. 2 is a schematic illustration of a controller of the helicopter ofFIG. 1;

FIG. 3 is a perspective view of helicopter engine inlets in accordancewith embodiments;

FIG. 4 is an axial view of a helicopter engine inlet with variablegeometry in accordance with embodiments;

FIG. 5A is a schematic axial view of the helicopter engine inlet of FIG.4 in a non-constricted condition;

FIG. 5B is a schematic axial view of the helicopter engine inlet of FIG.4 in a constricted condition;

FIG. 6 is an axial view of a helicopter engine inlet with variablegeometry in accordance with embodiments;

FIG. 7A is a schematic axial view of the helicopter engine inlet of FIG.6 in a non-constricted condition;

FIG. 7B is a schematic axial view of the helicopter engine inlet of FIG.6 in a constricted condition;

FIG. 8 is a schematic illustration of a moveable portion of thehelicopter inlets of FIGS. 4 and 5A, 5B or FIGS. 6 and 7A, 7B with ahinge element in accordance with embodiments;

FIG. 9 is a flow diagram illustrating a method of controlling thehelicopter inlets of FIGS. 4-7B in accordance with embodiments;

FIG. 10 is a schematic illustration of a passive movable portion of thehelicopter inlets of FIGS. 4 and 5A, 5B or FIGS. 7 and 7A,7B inaccordance with embodiments;

FIG. 11A is a schematic axial view of the helicopter engine inlet in anon-constricted condition in accordance with further embodiments; and

FIG. 11B is a schematic axial view of the helicopter engine inlet in aconstricted condition such that an alternative inlet is opened inaccordance with further embodiments.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

As will be described below, a single- or multiple-duct variable geometryhelicopter engine inlet is provided and includes a movable portion ofthe inlet such that a size of a capture area of the inlet can be varied.The movable portion includes an internal flow surface and an aerodynamicsurface for external flow to limit drag while the internal flow surfacevaries the inlet capture area and diffusion or convergence ratios. Thecapture area of the inlet can thus be varied to suit a current flightcondition. The movable portion can be provided on a top and/or a side ofthe inlet and may provide for an increased diffusion ratio in itsconstricted area position where such increased diffusion ratio may betolerated or desired at higher speeds due to the presence of rameffects.

With reference to FIGS. 1-3, a helicopter 10 is provided and includes anairframe 11. The airframe 11 is formed to define a cabin portion 12 anda tail portion 13. At a top or uppermost section of the cabin portion12, the airframe includes a main rotor section 14 and a variable areaengine inlet 15 (or “inlets” in the case of a multiple-duct engineinlet). At the tail portion 13, the airframe includes a tail rotorsection 16. The helicopter 10 further includes at least a main rotor 140rotatably supported in the main rotor section 14 and a tail rotor 160rotatably supported in the tail rotor section 16. Both the main rotor140 and the tail rotor 160 are rotatable relative to the airframe 11 togenerate lift forces and thrust forces.

The helicopter 10 also includes an engine 17 and a controller 18. Theengine 17 is disposed within an interior of the airframe 11 and isreceptive of air drawn into the interior of the airframe 11 through thevariable area engine inlet 15. The engine 17 is coupled to the mainrotor 140 and the tail rotor 160 and is configured to drive rotation ofthe main rotor 140 and the tail rotor 160 by way of gear trains inaccordance with combustion of a mixture of fuel and the air drawn intothe interior of the airframe 11. The controller 18 may be embodied as aflight control computer.

In accordance with embodiments, the controller 18 may include a memoryunit 180, a processing unit 181 and servo elements 182, which arecoupled to the variable area engine inlet 15. The memory unit 180 hasexecutable instructions stored thereon. When executed, the executableinstructions cause the processing unit 181 to determine whether acurrent flight condition is a hover, low-speed or high-speed flightcondition or whether there is an asymmetric condition in a multi-ductinlet and to operate the servo elements 182 to vary a capture area 150of the variable area engine inlet 15 in accordance with the determinedcurrent condition. That is, the controller 18 is configured to constrictthe capture area 150 of the variable area engine inlet 15 in accordancewith the current flight condition being a high-speed flight condition,to dilate the capture area 150 in accordance with the current flightcondition being a low-speed or a hover flight condition and to use acombination of constricted and unconstructed areas in multi-duct inletsto equalize flow conditions.

The variable area engine inlet 15 includes a pair of first inletportions 20 and a pair of second inlet portions 21. The first inletportions 20 are disposed to face one another in opposite directions andat a distance from one another. The second inlet portions 21respectively extend between the first inlet portions 20 and are disposedto face one another in opposite directions and at a distance from oneanother. The first inlet portions 20 may be oriented transversely or, insome cases, perpendicularly with respect to the second inlet portions21.

In accordance with embodiments and, as shown in FIG. 3, one of the firstinlet portions 20 may be provided as a section 201 of fuselage of theairframe 11 while the other of the first inlet portions 20 may beprovided as a horizontally oriented top wall section 202. In theseembodiments, one of the second inlet portions 21 may be provided as asection 203 of a main rotor pylon while the other of the second inletsections 21 may be provided as a vertically oriented side wall section204. In accordance with further embodiments, leading sides of the firstand second inlet portions 20 and 21 may include aerodynamic elements 22to limit drag on airflow flowing around the variable area engine inlet15.

As shown in FIG. 3 (and in FIGS. 4 and 6 to be described below), adistance between the section 201 of the fuselage of the airframe 11 andthe horizontally oriented top wall section 202 defines at least aninitial height H1 of the variable area engine inlet 15 and a distancebetween the section 203 of the main rotor pylon and the verticallyoriented side wall section 204 defines at least an initial width W1 ofthe variable area engine inlet 15. The initial height H1 and the initialwidth W1 may cooperatively define a non-constricted or dilated conditionof the capture area 150.

With reference to FIGS. 4-7B, at least one or both of the first inletportions 20 and/or the second inlet portions 21 may include a movableportion 23. The movable portion 23 is disposed to occupy and movebetween first and second positions. The first position is associatedwith a non-constricted condition of the capture area 150 of the variablearea engine inlet 15 and the second position is associated with aconstricted condition of the capture area 150.

That is, as shown in FIGS. 4, 5A and 5B, the movable portion 23 may beprovided as the horizontally oriented top wall section 202 or may be acomponent of the same. In such cases, the non-constricted condition isassumed when the current flight conditions are low-speed or hover flightconditions and the movable portion 23 is accordingly disposed such thata height of the variable area engine inlet 15 is defined as the initialheight H1. By contrast, the constricted condition is assumed when thecurrent flight conditions are high-speed flight conditions and themovable portion 23 is accordingly disposed such that the height of thevariable area engine inlet 15 is defined as a secondary height H2, whichis shorter than the initial height H1 due to the fact that thehorizontally oriented top wall section 202 has moved downwardly.

Similarly, as shown in FIGS. 6, 7A and 7B, the movable portion 23 may beprovided as the vertically oriented side wall section 204 or may be acomponent of the same. In such cases, the non-constricted condition isassumed when the current flight conditions are low-speed or hover flightconditions and the movable portion 23 is accordingly disposed such thata width of the variable area engine inlet 15 is defined as the initialwidth W1. By contrast, the constricted condition is assumed when thecurrent flight conditions are high-speed flight conditions and themovable portion 23 is accordingly disposed such that the width of thevariable area engine inlet 15 is defined as a secondary width W2, whichis shorter than the initial width W1 due to the fact that the verticallyoriented side wall section 204 has moved laterally.

In accordance with embodiments and, with reference to FIG. 8, theairframe 11 may include a hinge 230 by which the movable portion 23 iscoupled to the airframe 11. In such cases, the movable portion 23 isdisposed to occupy and move between the first and second positions bybeing driven to pivot about the hinge 230 by the servo elements 182 ofthe controller 18, which in some embodiments may be provided as asolenoid motor disposed proximate to the movable portion 23. It shouldbe understood that other embodiments exist for driving, moving orotherwise controlling the movable portion 23 to move between the firstand second positions. These other embodiments may include, but are notlimited to, moving the movable portion 23 in a translating motion inwhich the movable portion 23 does not pivot about any predefined axis orproviding the movable portion 23 with smart materials and changing theshape of the movable portion 23 by heating or electrifying the smartmaterials.

With reference back to FIGS. 1, 2 and 3, it is seen that the variablearea engine inlet 15 may be provided as a first (or starboard side)variable area engine inlet 151 and a second (or port side) variable areaengine inlet 152. In such cases, both the first and second variable areaengine inlets 151 and 152 provide air flow to the engine 17 and may becontrolled as described above by the controller 18. In particular, thecontroller 18 may be configured to independently vary respective captureareas 150 of the first and second variable area engine inlets 151 and152 in accordance with the current conditions by driving movements ofthe movable portion 23 in each of the first and second variable areaengine inlets 151 and 152. For example, during a yaw movement of thehelicopter 10 where flow asymmetries may result in distortions at theface of the engine 17, the controller 18 may dilate the slower movinginterior (relative to the yaw movement) one of the first and secondvariable area engine inlets 151 and 152 and constrict the faster movingouter (relative to the yaw movement) one of the first and secondvariable area engine inlets 151 and 152.

In accordance with further aspects of the invention and, with referenceto FIG. 9, a method of controlling a variable area engine inlet of ahelicopter is provided. The method includes determining whether acurrent flight condition is a hover, low-speed or high speed flightcondition (operation 30), constricting a capture area of the variablearea engine inlet in an event a result of the determining indicates thatthe current flight condition is the high-speed flight condition(operation 31) and dilating the capture area in an event the result ofthe determining indicates that the current flight condition is the hoveror low-speed flight condition (operation 32). As noted above, thedilating may include moving a horizontally and/or vertically orientedinlet portion of the variable area engine inlet to a first positionassociated with a non-constricted condition of the capture area and theconstricting may include moving the horizontally and/or verticallyoriented inlet portion to a second position associated with aconstricted condition of the capture area.

As shown in FIG. 9, the method may further include an independentvarying of respective capture areas of a multiple-duct engine inlet inaccordance with the current conditions and in response to a conditioncharacterized by asymmetric flows relative to the first and secondvariable area engine inlets 151 and 152 (operation 310).

In accordance with still further aspects of the invention and, withreference to FIG. 10, it will be understood that although thedescription provided above generally relates to cases in which themovable portion 23 is driven to move by the servo elements 182 of thecontroller 18, alternative embodiments exist in which movement of themovable portion 23 is not controlled by the controller 18 or anycomponent thereof and is, instead, at least partially passivelyresponsive to current flight conditions. For example, the movableportion 23 may be passively moved from the first position to the secondposition as a speed of the helicopter 10 increases in response tocorresponding increases in air flow pressures and/or speeds within thevariable area engine inlet 15. That is, the movement of the movableportion 23 may be driven by the increases in air flow pressures and/orspeeds within the variable area engine inlet 15. In such cases, as shownin FIG. 10, the movable portion 23 may be coupled to the airframe 11 byway of the hinge 230 and an elastic element 231. The elastic element 231is disposed to bias the movable portion 23 towards the first positionbut is configured to permit the movable portion 23 to move toward thesecond position in passive response to air pressures 232 increasingbeyond a predefined limit.

In accordance with further embodiments and, as shown in FIGS. 11A and11B, the movable portion 23 may be provided as a section 201 of fuselageof the airframe 11 or may be a component of the same. In such cases, thenon-constricted condition is assumed when the current flight conditionsare low-speed or hover flight conditions and the movable portion 23 isaccordingly disposed such that a height of the variable area engineinlet 15 is defined as the initial height H11. By contrast, theconstricted condition is assumed when the current flight conditions arehigh-speed flight conditions and the movable portion 23 is accordinglydisposed such that the height of the variable area engine inlet 15 isdefined as a secondary height H22, which is shorter than the initialheight H11 due to the fact that the section 201 of the fuselage hasmoved upwardly. In such cases, the movement of the section 201 of thefuselage may open an alternate inlet 153. This alternate inlet 153 mayprovide for airflow to be used in compartment cooling, transmission baycooling, etc. The alternate inlet 153 may also be used to pull off lowenergy boundary layer flow and to prevent the boundary layer flow frombeing ingested by the engine inlet to thereby increase engineperformance.

The variable area engine inlet 15 described above presents little to noperformance compromise in accommodating hover or low-versus high-speedflight conditions. Indeed, analyses of the above-described structureshave shown significant performance increases in hover with negligibleperformance differences during high-speed flight conditions.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

The invention claimed is:
 1. A dual variable area engine inlet of ahelicopter, comprising: a fuselage section; a horizontally oriented topwall section disposed to oppositely face the fuselage section at adistance; a main rotor pylon section extending between the fuselagesection and the horizontally oriented top wall section; verticallyoriented side wall sections respectively extending between the fuselagesection and opposite ends of the horizontally oriented top wall sectionand being respectively disposed to face opposite sides of the main rotorpylon section at a distance, the fuselage section, a leading side of thehorizontally oriented top wall section, the main rotor pylon section anda leading side of the vertically oriented side wall sections definingcapture areas with forward-most portions thereof being forward facingopenings through which airflow is drawn; and movable portionsrespectively disposed as components of the horizontally oriented topwall section within the capture areas to occupy and move between firstand second positions respectively associated with non-constricted andconstricted conditions of the capture areas and each being independentlymovable to reduce or increase respective heights of the capture areas.2. The dual variable area engine inlet according to claim 1, wherein themovable portions are respectively disposed as components of only thehorizontally oriented top wall section and are independently movable toreduce or increase only the respective heights of the capture areas. 3.A dual variable area engine inlet of a helicopter, comprising: afuselage section; a horizontally oriented top wall section disposed tooppositely face the fuselage section at a distance; a main rotor pylonsection extending between the fuselage section and the horizontallyoriented top wall section; vertically oriented side wall sectionsrespectively extending between the fuselage section and opposite ends ofthe horizontally oriented top wall section and being respectivelydisposed to face opposite sides of the main rotor pylon section at adistance, the fuselage section, a leading side of the horizontallyoriented top wall section, the main rotor pylon section and a leadingside of the vertically oriented side wall sections defining captureareas with forward-most portions thereof being forward facing openingsthrough which airflow is drawn; and movable portions respectivelydisposed as components of the vertically oriented side wall sectionswithin the capture areas to occupy and move between first and secondpositions respectively associated with non-constricted and constrictedconditions of the capture areas and each being independently movable toreduce or increase respective widths of the capture areas.
 4. The dualvariable area engine inlet according to claim 3, wherein the movableportions are respectively disposed as components of only the verticallyoriented side wall sections and are independently movable to reduce orincrease only the respective widths of the capture areas.